1. Technical Field
The technical field relates to a liquid crystal display that can adjust a brightness level in each of a plurality of division areas and a driving method thereof. More particularly, the technical field relates to a liquid crystal display which can differently adjust a brightness level of an image area displayed with an image and a brightness level of a blank area displayed with a black color when the displayed image and displayed blank area exist in one screen and a driving method thereof.
2. Description of the Background Art
In today's information-oriented society, electronic display devices play a very important role and various electronic display devices are extensively used in various industry fields. As a result, an electronic display device field has been developed and electronic display devices that meet the demands of this information-oriented society have been developed. In general, an electronic display device is an apparatus for transmitting a variety of information to a human being through the sense of sight. That is, an electronic display device is an electronic apparatus for converting electronic information signals input from various electronic apparatuses into light information signals, which are perceivable by sight and transmits visual information.
In these electronic display devices, an apparatus that displays a light information signal by emitting light is known as a light-emitting display device. Conversely an apparatus that displays a light information signal with light modulation by reflection, scattering, or interference is known as a light-receiving display device. A light-emitting display device can also be known as an active display device. Examples of active display devices include a cathode ray tube (CRT), a plasma display panel (PDP), an organic electroluminescent display (OELD), and a light-emitting diode (LED). A light-receiving display device can also be known as a passive display device. Examples of passive display devices include a liquid crystal display (LCD) and an electrophoretic image display (EPID).
The CRT, which is often found in a television or a computer monitor and has been used for the longest time, has the largest market share in terms of economical efficiency. However, the CRT has negative characteristics such as heavy weight, large bulk, and high power consumption.
Recently, because of lowered voltage requirements and reduced power requirements of various electronic devices and decreases in size, thickness, and weight of electronic apparatuses due to rapid progress of semiconductor technology, demand for flat panel-type display devices has rapidly increased. Accordingly, a flat panel-type display device such as a liquid crystal display (LCD), a plasma display (PDP), and an organic electroluminescent display (OELD) have been developed. Among these flat panel-type display devices, a liquid crystal display that has a decreased size, thickness, and weight in addition to a lower driving voltage and lower power consumption has been particularly sought after.
As described above, because a liquid crystal display is not a light emitting display, it requires a light source such as a backlight. In general, there are two types of backlights for a liquid crystal display: a direct type and a light guide plate type. The direct type backlight has several lamps disposed in a flat surface and constantly sustains a gap between a lamp and a liquid crystal panel by providing a diffusion plate between the lamp and the liquid crystal panel. The light guide plate-type backlight has a lamp located at the outside of a flat surface, such that light is applied to an entire surface of the liquid crystal panel from the lamp by using a transparent light guide plate.
To more effectively display moving images or movie images in a conventional liquid crystal display, a brightness level of the lamp of the backlight is adjusted depending on an average of gray levels of the input image data. That is, a brightness level of the lamp of the backlight is greatly adjusted when a bright image is input, compared with when a dark image is input.
However, in the conventional liquid crystal display, when an image area displayed with an image and a blank area displayed with a black color both exist in one screen, the brightness level of the image area and that of a blank area are simultaneously adjusted. Therefore, when a bright image is displayed in the image area, brightness levels of both of the blank area and the image area are highly adjusted. Thus, due to the increase of the brightness level of the black color of the blank area, there is a problem that the concentration and contrast ratio for the image area are deteriorated.